1. Technical Field
The present invention relates to a human privates washing apparatus for washing human bodies with hot water.
2. Description of Related Art
A conventional human privates washing apparatus of this kind is shown in FIG. 28 as disclosed in, for example, Japanese Patent Laid-Open Publication No. 5-33377 (1993). FIG. 28 is a schematic view showing a supply system of wash water, in which a water supply pipe 152 is connected with an upstream side of a pump 151 and an air mixing portion 153 is mixed with a downstream side of the pump 151. The air mixing portion 153 includes a cylindrical suction head 154 made of ceramic such that air delivered from a compressor 155 is mixed into water in the suction head 154. By this arrangement, wash water supplied from the water supply pipe 152 is pressurized by the pump 151 and proceeds to the air mixing portion 153. In the air mixing portion 153, air supplied from the compressor 155 is divided into fine portions so as to flow into the wash water. Then, the wash water having passed through the air mixing portion 153 proceeds to a heat exchanger 156. The wash water heated to a proper temperature by the heat exchanger 156 is supplied to a nozzle device 157 so as to be injected towards human privates. By this function, the wash water injected from the nozzle device 157 contains air bubbles and thus, mild bodily sensation is obtained at the time of washing of the human privates.
However, in the above mentioned conventional human privates washing apparatus, control of the compressor 155 and control of the heat exchanger 156 are not associated with each other. Therefore, if ratio of amount of the wash water to amount of air is not proper, a large amount of air is collected, thus resulting in local boiling or abnormal heating in the heat exchanger 156. Meanwhile, since control of the compressor 155 and control of the heat exchanger 156 are not integrated, a user should perform a plurality of operations and cannot fully operate the conventional human privates washing apparatus unless the user is skilled in operational sequences or timings corresponding to situations. Furthermore, such a problem arises that any measure for reducing power consumption is not taken.
Meanwhile, since air bubbles are integrated with each other so as to become larger in diameter while proceeding from the air mixing portion 153 to the nozzle device 157, hot wash water is injected intermittently from the nozzle device 157, thereby resulting in uncomfortable sensation during use or scattering of the wash water. In addition, such an inconvenience is incurred that it is impossible to lessen heating quantity through reduction of heat dissipation of the heat exchanger 156.
Conventionally, generally known water heaters for human privates washing apparatuses are divided into a hot water storage type in which a fixed amount of water stored in a tank is at all times heated to and kept at a proper temperature by a heater and an instantaneous heating type in which supplied water is instantaneously heated such that hot water heated to a proper temperature is fed. A hot water storage type water heater is shown in FIG. 29 as disclosed in Japanese Patent Publication No. 2-3860 (1990). In FIG. 29, a lid 163 is securely fixed to an upper open end of a hot water storage tank 161 of a water heater 162 by a fastening member (not shown). A water inlet pipe 164 is attached to the lid 163. One end of the water inlet pipe 164 is connected with a water supply source (not shown) via a water supply pipe 165, while the other end of the water inlet pipe 164 extends through the lid 163 to a vicinity of a bottom of the hot water storage tank 161. A hot water discharge portion 166 is attached to the lid 163 and has a hot water outlet 166a communicating with interior of the hot water storage tank 161. A heater 167 for heating water is inserted into the hot water storage tank 161 through the lid 163. Meanwhile, a temperature sensor 168 for detecting temperature of hot water is mounted on the lid 163 such that a temperature sensing portion 168a is inserted into the hot water storage tank 161. Power supply to the heater 167 is controlled in accordance with temperature of the hot water detected by the temperature sensor 168 such that the hot water in the hot water storage tank 161 is at all times kept at a preset temperature of, for example, about 40.degree. C.
However, in the conventional hot water storage type water heater of the above described arrangement, since the amount of stored hot water is limited, hot water having the preset temperature is supplied until the amount of discharged water exceeds the amount of stored hot water. However, if this water heater is used for a such a long time that the amount of discharged water exceeds the amount of stored hot water, temperature of the hot water starts to drop gradually. Namely, if the amount of discharged water exceeds the amount of stored hot water, most of the hot water heated by the heater 167 and stored in the hot water storage tank 161 is discharged from the hot water storage tank 161 and water having flowed into the hot water storage tank 161 after start of discharge of the hot water is discharged. As a result, temperature of the hot water discharged from the hot water storage tank 161 starts to drop gradually. This happens because water having flowed into the hot water storage tank 161 immediately after start of use of the hot water is heated to vicinity of the preset temperature to some extent but water having subsequently flowed into the hot water storage tank 161 is discharged almost without being heated. Hence, since hot water having a temperature lower than the preset temperature is discharged, there is a risk that uncomfortable sensation is given to a user during washing of the body. Therefore, the hot water storage type water heater 162 has such a drawback that since the water heater 162 can be used only for a case in which period for discharging hot water is short, the human body cannot be washed satisfactorily with hot water having the proper temperature unless washing period is shortened and the water heater 162 is used intermittently.
In order to solve the above described problems in case the hot water storage tank 161 of the hot water storage type water heater 162 cannot be made large, an instantaneous heating type water heater disclosed in, for example, Japanese Utility Model Publication No. 1-42757 (1989) as shown in FIG. 30 is adopted. A water heater 179 shown in FIG. 30 is constituted by a metallic heating tank 180 formed into a cylindrical shape having a bottom and a hot water storage cylinder 181 formed into a hollow cylindrical shape. The heating tank 180 is accommodated in the hot water storage cylinder 181 such that a hot water storage portion 181a is defined above the heating tank 180. An open end of heating tank 180 is fitted into one opening of the hot water storage cylinder 181 such that the heating tank 180 is communicated with the hot water storage cylinder 181 via a through-hole 182 formed on a peripheral edge of the heating tank 180 adjacent to the open end. Then, a hollow cylindrical ceramic heater 183 including an electric heating element formed by performing printing on its surface or between two ceramic substrates is communicated with a water supply line (not shown) so as to be loosely fitted thereinto. The opening of the hot water storage cylinder 181 is closed by a flange of the ceramic heater 183. The other opening of the hot water storage cylinder 181 is closed by a housing 186 including a float switch 184 and a vacuum switch 185 such that the housing 186 is communicated with the hot water storage cylinder 181. Thus, hot water is discharged from a hot water discharge pipe 187 fixed to the housing 186. A temperature sensor 188 for detecting temperature of hot water heated by the ceramic heater 183 is mounted above the through-hole 182 formed on the heating tank 180.
In the instantaneous heating type water heater 179, since water proceeding through an inner periphery of the ceramic heater 183 into the heating tank 180 can be instantaneously heated to a preset temperature by the electric heating element of the ceramic heater 183, namely, the water flowing into the heating tank 180 can be continuously heated to the preset temperature during flow of the water, hot water having a fixed temperature can be continuously discharged for a long time advantageously. On the other hand, breakers for protecting overcurrent are installed on houses in general. In order to prevent trip of the breakers, wattage of the heater should be set to be not more than about 1200 W at AC 100 V. In case hot water having, for example, 40.degree. C. is used, discharge rate should be not more than about 400 cc/min. in order to raise temperature of water by 40 degrees in view of winter season in which temperature of water supplied to the water heater is low. In the instantaneous heating type water heater of the above described arrangement, as diameter of the hollow cylindrical ceramic heater 183 is reduced further, production of the ceramic heater 183 becomes more difficult and its heat transfer area becomes smaller, so that there is a limit to diameter of the ceramic heater 183. Therefore, water storage portions in which water is collected are produced in water passages of the heating tank 180, the hot water storage cylinder 181, etc. which have volumes corresponding to size of the ceramic heater 183. For example, even if discharge rate is about 200 cc/min., its thermal capacity becomes large due to the water storage portions and water is collected in the water storage portions which are not so small as the discharge rate of not more than about 400 cc/min. As a result, such a disadvantage is incurred that since not only a long time period is required for raising temperature and effecting response in temperature control but flow velocity becomes small due to large cross-sectional areas of inner and outer peripheral flow paths of the ceramic heater 183 as compared with the above discharge rate, heat transfer rate deteriorates, thereby resulting in deterioration of thermal efficiency of the water heater.
Meanwhile, in addition to the inconvenience that period for discharging hot water is limited, the human privates washing apparatus including the above mentioned hot water storage type water heater has a drawback that the apparatus becomes large in size due to the hot water storage tank and a disadvantage that since power supply should be performed all day long such that the apparatus can be used any time, loss caused by heat dissipation due to storage of hot water occupies a major portion of whole power consumption, thus resulting in extreme rise of its running cost. On the other hand, the human privates washing apparatus including the instantaneous heating type water heater of the above described arrangement has been disadvantageous in that since volume of the heating tank becomes large due to size of the hollow cylindrical ceramic heater, it is difficult to make the apparatus compact and that since control response is poor due to the water storage portions, it is difficult to instantaneously change set temperature during washing.
In addition, conventionally, a flow rate sensor and a human privates washing apparatus including the flow rate sensor are disclosed in, for example, Japanese Patent Laid-Open Publication No. 6-264486 (1994) as shown in FIG. 31. The conventional flow rate sensor is described with reference to FIG. 31. FIG. 31 is a cutaway front elevational view of the flow rate sensor. In FIG. 31, a flow rate sensor 201 is constituted by a body 204 having an inflow path 202 and an outflow path 203, an impeller 206 rotatably supported by a shaft 205 mounted on the body 204 and a photo interrupter 207. The photo interrupter 207 is disposed at such a position that its optical axis passes through a peripheral edge of a side plate 208 provided on the impeller 206. Light is intercepted by the side plate 208 but passes through a plurality of recesses 209 formed on a peripheral edge of the side plate 208 at regular intervals such that the number of revolutions of the impeller 206 is detected.
Meanwhile, FIG. 32 is a piping diagram of a human privates washing apparatus including this flow rate sensor. In FIG. 32, a hot water storage tank 212 incorporating a heater 211 is connected with a downstream side of a water supply pump 210. Meanwhile, a washing nozzle 213 for injecting wash water to human privates is connected with a downstream side of the hot water storage tank 212 through a flow rate sensor 201. On the basis of flow rate expressed by the number of revolutions of the impeller 206 and its variations delivered from the flow rate sensor 201, a controller 214 controls drive voltage of the water supply pump 210.
However, in the known flow rate sensor of FIG. 31, since wash water for rotating the impeller 206 flows rectilinearly from the inflow path 202 to the outflow path 203, fluidal force for rotating the impeller 206 is insufficient. Therefore, at the time of low flow rate, the impeller 206 is likely to be not rotated or be rotated unstably disadvantageously. Meanwhile, if air bubbles have adhered to the impeller 206 in some form or other, the air bubbles are integrated in the vicinity of a rotary center of the impeller 206 by centrifugal force produced by rotation of the impeller 206, so that such problems arise that it is difficult to discharge the air bubbles outwardly and rotations of the impeller 206 become unstable, thereby resulting in drop of accuracy of detection of flow rate.
Meanwhile, in the conventional human privates washing apparatus of FIG. 32, since power supply to the heater 211 should be performed at all times in order to maintain temperature of wash water in the hot water storage tank 212, loss of power consumption is caused by heat dissipation. In addition, since air dissolved in the wash water in the hot water storage tank 212 is likely to appear as air bubbles upon heating and the air bubbles flow into the flow rate sensor 201, a large error is produced in value of detected flow rate due also to the above described problems.